Foreign currency is a term used to describe a currency that is not the country's official currency. There are several synonyms for the term "foreign currency." One of the most commonly used is "foreign exchange," often abbreviated as "forex." This term refers to the trading of currencies between different countries. Another synonym for foreign currency is "currency exchange," which refers to the process of exchanging one currency for another. Other synonyms include "non-native currency," "alien currency," and "overseas currency." The use of these synonyms varies depending on the context of the discussion. However, they all refer to currencies that are different from the country's official currency.